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The "A*" is probably a matter of notation. The bright stuff at the center has been called "Sagittarius A" for quite some time, and once resolution improved they discovered it had two parts, a hypernova remnant and something else I forget--these are "Sagittarius A East" and "West." Further improved resolution came up with a superpowerful radio point--and, with a point nestled within Sagittarius A, it wouldn't be too much of a stretch to assign it a "*" to indicate this.
This is just conjecture; I'm not an astronomer. --The Centipede — Preceding unsigned comment added by 165.134.186.199 (talk • contribs) 01:24, 13 April 2005 (UTC)
Is this object going to erupt in 10 million years? Xaxafrad 05:51, 11 December 2006 (UTC)
Later observations determined the mass of the object to be about 3.7 million solar masses within a volume with radius no larger than 6.25 light-hours (45 AU) or about 4.2 billion miles. For comparison, Pluto orbits our Sun at a distance of 5.51 light-hours or 3.7 billion miles.
This is compatible with, and strong evidence in support of, the hypothesis that Sagittarius A* is associated with a supermassive black hole. While it is possible for the observed mass within the observed volume limit to be distributed among multiple objects, any such objects would undergo orbital collapse into a single black hole anyway within a few hundred years at most, a negligible amount of time compared with the lifetime of the galaxy.
45 AU is 180 times more radius than is necessary for 3.7 million solar masses to not need to be a black hole. It doesn't matter if it's one body or many. That is enough space so that it could be any number of stable systems which aren't black holes, and which need never become a black hole. The last sentence of this passage is wrong for many reasons. --76.224.88.42 (talk) 18:07, 20 December 2007 (UTC)
The first paragraph implies that only in 2002 was it discovered this source is a compact object (ie a black hole). In fact, work has been going on for decades toward this end, this includes work of Genzel, Ghez and other researchers. Sgr A* is in every astronomy textbook as a black hole. As written, the article wrongly attributes full credit for discovery of the black hole to one researcher, and was likely written to promote that researcher's work. Attribution should be secondary to a good description of the object itself. If this is not fleshed out better to include previous research, I will remove the specific attribution, and just say "astronomers have determined" etc. Substar (talk) 15:49, 14 April 2008 (UTC)Substar
I'm confused. The article for this, and the article for the Galactic Center, both seem to make a distinction between Sagittarius A* and the supermassive black hole at the center of the Milky Way. The way it seems, "Sagittarius A*" is more of a name for the general area, or for the radio and x-ray emmissions of the accretion belt of the black hole, and the reason for the distinction is that we haven't seen the black hole itself.
Why is there the distinction? I always thought of "Sagittarius A*" as the name of the black hole itself. If Sagittarius A* doesn't stand for the black hole, then does the black hole have any sort of name? Should the central black hole have it's own article or anything? I'm just curious. Shnakepup (talk) 16:31, 26 June 2008 (UTC)
I like to look up into the sky and recognise stories, myths and cosmologies that the heavens provide. It would be nice if someone provided a constellation map of the Sagittarius that showed which visible stars that approximates the centre of our galaxy. —Preceding unsigned comment added by Xact (talk • contribs) 01:31, 23 January 2008 (UTC)
It's pretty much where the steam would be leaving the spout of the teapot. Look on the net for photos of Sagittarius against the Milky Way. The brightest spot near the spout is the centre of the galaxy - and thats where Sgr A* is. —Preceding unsigned comment added by 61.68.176.2 (talk) 11:12, 8 December 2008 (UTC)
Even if it's not a supermassive black hole, has anyone approximated the age of Sagittarius A*? --Yoshiaki Abe (talk) 04:24, 1 September 2008 (UTC)
The article cites a VLBI image "the edge of the event horizon". I have been unable to locate any source for such a claim. I do not argue the veracity, I merely wish more detailed information, and hope the source will provide it. I would deeply appreciate any direction.Azutjw (talk) 20:37, 11 November 2008 (UTC)
The same findings were published in the September 27 issue of Science News (http://www.sciencenews.org/view/generic/id/36161/title/Milky_Ways_black_hole_seen_in_new_detail), where they clearly state Sagitarrius A* is located off-center from the supermassive black hole. Given this information, I believe sections of this article referring to the theory that Sagitarrius A* is the black hole at the center of our galaxy should be removed to reflect the realities of the latest research. - King's English —Preceding unsigned comment added by Kings english (talk • contribs) 15:33, 27 April 2009 (UTC)
There is no evidence proving that it is a black hole. There is only evidence that it is a supermassive object somewhere nearby but it's size is not known. Also it's mass is only deduced based on movements of other objects and we all know interpretation of such movements is far from straightforward as results contradict general relativity unless speculative dark matter is introduced. All this means that we don't know what it is, it may be a black hole (if they can even exist, singularities are a very strong argument against their existence, especially since cosmic censorship hypothesis has been disproved) or it may be some other exotic object, it may be an object whose nature we are not able to understand yet. We still don't have a theory combining quantum mechanics and general relativity, such a theory once discovered may significantly alter our understanding of cosmology. In any case there is no evidence to support the claim that central mass of Sagittarius A* "must be a black hole, beyond any reasonable doubt" only that it must be a supermassive object and it's certainly not the same thing.Sergiacid (talk) 04:50, 19 May 2009 (UTC)
This article seems to have fallen victim to one of the more annoying mistakes that can be found on Wikipedia: quoting a source that supposedly buttresses the stated fact, but which in fact does not. I am speaking of how the mass of Sagittarius A* prime has a mass of 3.7 million suns. In fact, both reference #5 and #7 say it is 4.1 million suns. Specifically, Ref. #5, The First Measurement Of Spectral Lines In A Short-Period Star Bound To The Galaxy’s Central Black Hole: A Paradox Of Youth states that its mass is 4.07 ±0.62 million, which they roughed to 4.1 ±0.6 million in the abstract of the paper. Further, Ref. #7, UCLA Galactic Center Group, also says it is 4.1 million solar masses.
I’ve corrected the article accordingly. Greg L (talk) 05:58, 21 May 2009 (UTC)
Now, the BBC series "Horizon" (broadcast November 3rd, 2009) discusses Black Holes, and also notes that Sagittarius A* is (circa) 4.31 million times heavier than the Sun. Basing on this, I have put an approximate median for the Black Hole as:
8,573,021,000,000,000,000,000,000,000,000,000,000,000,000kg
or... 8,573,02136
I calculated this by multiplying 1,989,100,000,000,000,000,000,000,000,000kg (The mass of the sun) by 4,310,000,000.
-- OsirisV (talk) 23:30, 3 November 2009 (UTC)
I added some info from the cited papers about how the observations of S2 (and nearby stars) were made with NIR interferometry. The fact that such observations could be made at all, given the enormous density of stars, gas and dust along the line-of-sight from Earth to the galactic centre is really astounding to me. If anyone is knowledgeable enough to expand on this, in my POV it would be informative to explain just how technically challenging these observations are. Also, I got the impression from the refs that measuring the distance to the galactic centre very accurately, which was also accomplished by these observations, is important in astronomy for the calibration of distance scales, so I added this. Puzl bustr (talk) 21:05, 8 December 2009 (UTC)
Why exactly is the merge being proposed? I'm not saying that it would be a _bad_ thing, I just don't see what's wrong with the current situation.
If a substantial number of lurkers come forward in favour of the merge, I'll be happy to merge it, but I'd prefer not to bother. --Christopher Thomas 05:10, 27 March 2006 (UTC)
I came to this article look specifically for information on Sagittarius A*. Merging would be confusing and all together pointless Nintenfreak 21:51, 30 March 2006 (UTC)
No merge... above arguments say it all. Sagittarius A* is the ultimate hub of our galaxy, and is deserving of a wikipedia survey peg. NevilleDNZ 09:40, 4 April 2006 (UTC)
No merge, A* is a more specific feature Zzzzzzzzzzz 00:13, 13 April 2006 (UTC)
I also believe that the two articles shouldn't be merged, because Sagittarius A simply refers to the area (and objects within it) where the radio emissions that were detected by the Bell Telephone Laboratories (as shown here) are coming from. Because the objects are so critically different there would be a large amount of confusion between the two. — Preceding unsigned comment added by Smulumudi (talk • contribs) 00:18, 9 June 2011 (UTC)
I've removed the merge templates, as we've had 3 votes against and one abstention since the merge was proposed. --Christopher Thomas 18:43, 14 April 2006 (UTC)
Anyone know the radius of the event horizon of such a black hole? Just wondering how close S2 (star) comes. --Doradus (talk) 15:47, 4 April 2008 (UTC)
I just noticed a possible problem with this graphic - which is otherwise great, and many thanks to wikipedian Cmglee for making it. (Full disclosure, I certainly ain't no astronomer :-) so forgive me if I screw this up.).
I think the x-axis scale (Right Ascension, in hours, minutes, and seconds, with the darker scalelines 0.1 seconds and the smallest division 0.02 seconds) and the y-axis scale (Declination, in degrees, minutes, and seconds, with again the darker scalelines 0.1 seconds and the smallest division 0.02 seconds) may be messed up. Having looked up Right Ascension and Declination in (of course) wikipedia, it turns out that Declination is normally scaled in arcseconds (360 degrees in a circle, each divided into 60 arcminutes, each divided into 60 arcseconds - so 360x60x60=1,296,000 arcseconds in a full circle). However, Right Ascension is *not* scaled in arcseconds; instead it is in "seconds of Right Ascension", and 1 second of Right Ascension is actually 15 arcseconds. (From Wikipedia on Right Ascension: "a second of right ascension equal to 15 seconds of arc."). Actually, this makes sense; for Right Ascension, there are 24 hours, each divided into 60 minutes of Right Ascension, each divided into 60 seconds of Right Ascension, so: 24x60x60 = 86,400 seconds of Right Ascension in a full circle. But since 1 second of Right Ascension = 15 arcseconds, then 86,400 x 15 = 1,296,000 arcseconds in a full circle, ok, it all fits. So the graphic x-axis scale is distorted? I see two options:
(a) the y-axis, Declination, is in tenths and hundredths arcseconds, but the x-axis, Right Ascension, is in tenths and hundredths of seconds of Right Ascension, units which are 15-fold bigger. Or, alternatively,
(b) both scales are in arcseconds, and the X-axis is improperly labelled. Arrrrgh.
My guess is (b). This all stems from the confusion that you (or me, a definite amateur) would think a "second" would only have one meaning when working in the equatorial coordinate system on the celestial sphere, but really it has two meanings. Bad choice of terminology, darn those astronomers, but it's no doubt too late to change. Better to discuss Declination in "seconds of arc" or "arcseconds", but Right Ascension in "seconds of Right Ascension", where 1 second of Right Ascension equals 15 arcseconds. Sheesh. So, anyway, I think the graphic needs fixing, but I'm not brave enough to try it myself. I hope Cmglee or somebody can address this. My guess is that the x-axis should be relabelled, and I suspect it should really be "Right Ascension difference (in arcseconds) from RA 17h 45m 40.045s (note, 15 arcseconds = 1 second of Right Ascension)". Similarly, the y-axis might be relabelled "Declination difference (in arcseconds) from Decl -29 deg 0' 27.9" " Also, the long-form caption as it appears in the < File:Galactic centre orbits.svg > page (but not in the main Sagittarius A* article) should also be fixed, assuming I've got all this straight, so as to make the scale on both axes in arcseconds more clear.
By the way, it was *brilliant* to put the small Solar System / Sedna / Eris / Neptune / Pluto down there in the lower righthand corner for scale comparison. To further improve it, perhaps the short form caption in the main page (and the long form caption in the < File:Galactic centre orbits.svg > page should be amended to include something like: "In the small Solar System scaling graphic at the lower right, Pluto's orbit is the smallest near-circle, about 30-49 AU, and the long, very off-center ellipse is Sedna's orbit, with aphelion 937 AU and perihelion 76 AU."
Also, in the long form caption, there is "the scale is assumed to be 7940 AU/arcsecond"; the new Nature paper (see "dustcloud" below) has an improved number, based on a revised distance of 8.33 kpc to Sagittarius A*, and now it should probably be 1 arcsecond = 40 mpc = 1.25 × 10e17 cm = 8,251 AU; other stuff there would also need to be fixed accordingly. Also in that long form caption, it would be clearer to say that the separation between bold lines (0.1 arcseconds) represent about 825 AU. Let me know if this all makes any sense. Thanks. - lanephil Lanephil (talk) 20:21, 20 December 2011 (UTC)
Today in the New York Times it is reported that a dust cloud is headed to impact (or else come really close to) the presumed black hole at the center of Sagittarius A*, with impact (or close approach) to be visible to Earth-based telescopes (infrared telescopes on the ground and in orbit, and X-ray telescopes in orbit) in 2013. See < http://www.nytimes.com/2011/12/20/science/forecast-for-sagittarius-a-black-hole-a-cold-gas-cloud.html?ref=todayspaper >. See also "A gas cloud on its way towards the supermassive black hole at the Galactic Centre", S. Gillessen et al, Nature, doi:10.1038/nature10652, published online 14 December 2011 [actual hardcopy publication date, volume, page number TBD; < http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10652.html > ]. Could somebody insert a section stating this? It'll be VERY cool to see the pics and videos that come out of that. Thanks. - lanephil Lanephil (talk) 20:32, 20 December 2011 (UTC)
Article currently has "The radius of the central object must be significantly less than 17 light hours, because otherwise, S2 would either collide with it or be ripped apart by tidal forces". But the radius of a body of a particular mass does not classically affect the tidal field at a particular greater distance - can things be much different here? 94.30.84.71 (talk) 15:55, 27 June 2012 (UTC)
I have read that a gas cloud will pass near Sgr A* in mid-2013 (ERT), and be significantly disrupted. If true, that seems worth mentioning. 94.30.84.71 (talk) 15:58, 27 June 2012 (UTC)
The page Supermassive black hole seems to be based on newer research and mentions a mass of 3.6 millions times the mass of the Sun. See also the UCLA article linked from there. --Andrei Badea 10:19, 17 April 2006 (UTC)
i have also a problem with this: "The radius of the central object must be significantly less than 17 light hours, because otherwise, S2 would either collide with it or be ripped apart by tidal forces. In fact, recent observations[16] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit, leading to density limit 8.55×10^36 kg / 1.288×10^39 m^3 = 0.0066 kg/m^3"
now, compare that 0.0066 kg/m^3 with earth calculated density 5.515 g/cm^3 ... wow! ordinary earth matter density many times more that a black hole!? we live on a superdense black hole already?Totedati (talk) 08:34, 16 July 2012 (UTC)
A new star with an even shorter orbit than S0-2: S0-102. [1] 46.126.76.193 (talk) 21:06, 6 October 2012 (UTC)
Yeah! cmɢʟee'τaʟκ, save us! Please add S0-102 to your awesomely pretty chart! Zirconscot (talk) 13:28, 7 October 2012 (UTC)
"A typical neutron star has a mass between 1.35 and about 2.0 solar masses [1][2], with a corresponding radius of about 12 km" from Neutron star. So 4.1 million solar mass of neutron star density would have about 20000km radius, or 1/7 light second of diameter - its 100000 smaller than limit from this articles, like 6.25 light hours ... ? — Preceding unsigned comment added by 89.78.183.53 (talk) 18:50, 17 October 2011 (UTC)
A LOT of problems with this article and this talk page. First as far as I know (not that much, I admit) a black hole is the region around a gravitationally collapsing singularity bordered by its event horizon. Not necesaarily including its ergosphere. Second, it is an assumption that neutron degeenerate matter will collapse into a singularity (upon reaching a certain mass). The discussion about neutrons stars, quark stars, and black holes is highly speculative. SagA* is a REAL world observable, not a theoretical construct, and should be kept logically separate from the speculation (even tho' it is based on our best current science) that it constains a black hole. As far as we know there is nothing to prevent a neutron star from collapsing into a singularity, but until we have a plausible quantum gravitational theory, it is really quite radical to assume there is no other explanation for our observations. Absence of evidence is not evidence of absence. Small, dense, with lensing does not require the conclusion that it is a singularity. The point being there may be additional states of matter beyond neutron/quark densities but less than the infinities of a singularity. Other issues seem secondary. Needs Improvement71.31.149.224 (talk) 23:14, 1 July 2012 (UTC)
See https://medium.com/the-physics-arxiv-blog/bb5ae64fa4fa, hat tip http://science.slashdot.org/story/14/05/14/1620225/supermassive-black-hole-at-the-centre-of-galaxy-may-be-wormhole-in-disguise — Preceding unsigned comment added by 151.191.175.205 (talk) 22:05, 14 May 2014 (UTC)
Much of what is written in this (and other articles on Wiki) is indecipherable without expert knowledge. What's the point? If people have to take a degree in physics just to read a few paragraphs the article becomes irrelevant except to those already educated in the subject.
I'm not saying remove the techinal detail and jargon but perhaps an encyclopedia should attempt to explain subjects in language accessible to all, not just scientists.
I'm a software engineer, I often have to modify the language I use to avoid the "glazing-over" effect even when talking to people familiar with IT concepts. It takes a little effort but it's worth it to be understood.
Thanks Steve — Preceding unsigned comment added by 2.124.56.236 (talk) 12:04, 22 September 2014 (UTC)
"First noticed as something unusual in images of the centre of our galaxy in 2002,[24] the gas cloud G2, which has a MASS ABOUT 3 TIMES THAT OF THE EARTH, was confirmed to be likely on a course taking it into the accretion zone of Sgr A* in a paper published in Nature in 2012.[25] Predictions of its orbit suggest it will have a closest approach to the black hole (a perinigricon) in mid to late 2013. At this time the gas cloud will be at a distance of just over 3000 times the radius of the event horizon (or ~260 AU, 36 light hours) from the black hole. Opinions differ as to the effect this might have on both G2 and the black hole. G2 appears to already be being disrupted over the past 3 years of observation,[25] and may be completely destroyed by the encounter. If this is the case a significant amount of it may be accreted by Sgr A* which could lead to a significant brightening of X-ray and other emission from the black hole, likely to last over the next several decades. Other astronomers have suggested the gas cloud may be hiding a dim STAR, OR EVEN A STELLAR MASS black hole, which would hold it together against the tidal forces of Sgr A* and the ensemble may pass by without any..."
isn't Sagittarius A* the name of the black hole rather than its location?Huritisho (talk) 08:00, 26 September 2015 (UTC)
I'd just like to mention, based on a few calculations... The star that collapsed to form this black hole had a total mass a trillion times the mass of our Sun. Yet, after the supernova, less than one millionth of the mass remained in the black hole, and the rest of the mass, about 10^69 GeV, was thrown out into orbit and formed the Milky Way Galaxy. Clouds of gas and dust cooled and collapsed into new stars and planets, and over billions of years, the black hole took in some of that mass and is now at its current mass, about 10^63 GeV, about a millionth the mass of the galaxy. Let's not forget our galaxy's true parent, the star that died to form this black hole. Zuloo37 (talk) 23:27, 3 December 2014 (UTC)
This is definitely not how the Milky Way was formed...178.15.151.163 (talk) 12:07, 10 February 2016 (UTC)
Supermassive black holes don't form in a single event. ElPeski (talk) 13:09, 25 June 2016 (UTC)
Currently the article provides two contradictory estimates of the mass (4 million solar masses and 1 mil. s.m) while incorrectly claimiing them to be "consistent". Furthermore, the abstract for ftn. 22 actually states about 3.6 M, not 1 M.
Link to abstract of ftn. 22: http://www.aanda.org/articles/aa/abs/2009/28/aa10922-08/aa10922-08.html
Current text below.
Someone who understands astronomy better than me needs to fix this. Yabti (talk) 16:23, 18 January 2016 (UTC)
"The mass of Sagittarius A* has been estimated in two different ways. 1.Two groups—in Germany and the U.S.—monitored the orbits of individual stars very near to the black hole and used Kepler's laws to infer the enclosed mass. The German group found a mass of 4.31 ± 0.38 million solar masses,[2] whereas the American group found 4.1 ± 0.6 million solar masses.[3] Given that this mass is confined inside a 44 million km diameter sphere, this yields a density ten times higher than previous estimates. 2.More recently, measurement of the proper motions of a sample of several thousand stars within approximately one parsec from the black hole, combined with a statistical technique, has yielded both an estimate of the black hole's mass, and also of the distributed mass in this region. The black hole mass was found to be consistent with the values measured from individual orbits; the distributed mass was found to be 1.0 ± 0.5 million solar masses.[22] The latter is believed to be composed of stars and stellar remnants."
Would be interesting to indicate the history of the determination of the center of the Milky Way . — Preceding unsigned comment added by Chiloa (talk • contribs) 16:20, 1 June 2017 (UTC)
Science News, original publication. I'm not sure how to include it, but as it is closely connected to the central black hole I think it should get included in the article. --mfb (talk) 20:13, 4 September 2017 (UTC)
I was looking at the first paragraph and Wikipedia in general, why is Sagittarius A* always referred to as a radio source first and then further into the article Sagittarius A* is described as a potential black hole? Isn't the evidence at this point overwhelming that it is indeed a black hole? Is this just a case of Wikipedia not being updated yet for the most current information? I've included some good links below that refer to Sagittarius A* as a black hole first a foremost. I originally posted this in the talk section for S-2, but figure it probably will be of more use here.
https://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html https://www.britannica.com/topic/Sagittarius-A-black-hole http://chandra.harvard.edu/photo/2015/sgra/ https://news.nationalgeographic.com/2017/04/black-hole-event-horizon-telescope-pictures-genius-science/ https://arxiv.org/pdf/1707.01937
143.165.48.50 (talk) 16:30, 12 March 2018 (UTC)
https://en.wikipedia.org/wiki/List_of_black_holes (interestingly on Wikipedia's own list of black holes it is named Sagittarius A*) 143.165.48.50 (talk) 14:03, 13 March 2018 (UTC)
I just find an article and it have some more list of stars orbiting Sgr A*. Here is the link:[arxiv.org/pdf/astro-ph/0306130] but I'm not good at html and siting sources. Anybody knows how to site sources?Ydon205 (talk) 20:33, 26 November 2014 (UTC)(my english is not good)
For someone who has the patience to do the edit, there is also this as of April 2018, a dozen smaller black holes discovered orbiting Sgr A*: https://scitechdaily.com/astrophysicists-discover-dozen-black-holes-orbiting-sgr-a/ — Preceding unsigned comment added by Richwilkinson (talk • contribs) 01:11, 31 May 2018 (UTC)
The current version of the article states that "... the radio source of Sagittarius A * is symmetrical.[30] These results are at tension with General Relativity which if no other viable explanation is found within the general relativistic paradigm may demand a new theory of gravitation or modifications to General Relativity itself". However, when checking the scientific article cited, the abstract (and hence the article itself) totally contradicts any tension with General Relativity. In fact, the abstract clearly indicates "We show that multiple disk-dominated models of Sgr A* match our observational constraints, while the two jet-dominated models considered are constrained to small viewing angles". This is, they model the get using General Relativity and find plenty of models. Maybe the sentence about the tension with General Relativity must be deleted. — Preceding unsigned comment added by 2001:F40:902:C02F:7126:81E2:DE37:373B (talk) 18:05, 6 April 2019 (UTC)
Images have been added to the black hole section, but the earlier observations section needs to be updated, as they refer to such observations in the future. I lack the proper knowledge to do a proper fix myself, as it requires more than just a verbe tense change- probably a summary of the papers. --jynus (talk) 20:08, 10 April 2019 (UTC)
The added image is not Sgr A*, but the black hole at the center of M87. See https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7
On 31 October 2018, a paper was published that confirmed there is a black hole at Sgr A*. Most of the "Central black hole" section states clearly that the existance of the black hole is not certain, but all of those articles are years old. Our knowledge has changed; with new telescopes, new techniques of observation, and direct observation of dust which proves the existence of the black hole. The "Central black hole" section should be revised to remove the outdated statements of uncertainty. I will start my version of this revision in about nine hours because I must go to work now. Nick Beeson (talk) 14:14, 12 November 2018 (UTC)
References
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The article currently says: "In 2016 direct radio images were taken of Sagittarius A* by the Event Horizon Telescope, processed and published on April 10, 2019."
But, those images are of M87*, not Sagittarius A*. I looked at the source cited with this statement, but it makes no mention of images of Sagittarius A*. 82.176.221.176 (talk) —Preceding undated comment added 05:44, 11 April 2019 (UTC)
At least according to some YouTube comments here: https://www.youtube.com/watch?v=VnsZj9RvhFU&lc=UgzirMx3SeVrODV8Myh4AaABAg ;) --2A02:AA16:3882:3680:7CEF:CC6C:8208:3480 (talk) 20:13, 10 April 2019 (UTC)
This recent article updates the mass estimate for the SMBH to (3.964±0.047±0.026) solar masses and the distance to 7946±50±32 parsec.
Published: Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole or freely available pre-print.
Could someone familiar with editing and citing in Wikipedia incorporate this.
Thanks, George Dishman (talk) 07:59, 1 September 2019 (UTC)
I think it's against WP:INDISCRIMINATE to have the huge list in Sagittarius A*#Orbiting stars. I'll remove it in a couple of days unless anyone objects. Sam-2727 (talk) 00:44, 5 October 2019 (UTC)
S0–102 should be in this chart. What name should it have ?
S0? or something else? --Io Herodotus (talk) 14:25, 16 January 2020 (UTC)
". . . this yields a diameter of 60 million kilometres." — Is this saying that the diameter of the black hole at the center of the Milky Way galaxy is 60 million kilometres? Google tells me something about 23.6 million kilometers. I don't really know this topic at all, by the way. I just don't understand what is what and if there is a disagrement of information or . . . what all. — Preceding unsigned comment added by Kibbled Jive Elk Zoo (talk • contribs) 12:41, 7 October 2020 (UTC)
Please do not change the introduction to add doubt about the black hole; doing so is publishing original research. If you harbor doubts, then publish a paper in a reputable science journal, and get someone else to add your doubts with reference to that paper.
There use to be doubt, but time and data move on. This issue is entirely settled. If you do not agree, I repeat, find a counter-paper, published after the 2018 paper by Abuter, et al. Since Abuter was published no paper has been published in a reputable science journal that expresses any doubt. In fact, many papers have been published since Abuter that explicitly speak about the Sagittarius A* black hole, many in the title, and no one has challenged this in print. Nick Beeson (talk) 13:35, 19 August 2020 (UTC)
proofis incorrect, at least as I understand the term. Note that the reference you cite does not use the word "proof". We certainly have consensus (nothing else we know matches the parameters), but as best I know, we do not have a solid reference proving that the 4-million solar mass is a black hole. Note that matching some predictions for a black hole does not itself prove it is a black hole - after all, my TV matches some predictions for black magic, but that does not prove the existence of black magic. It's pedantry, but in an encyclopedia, important pedantry to avoid naming a "proof" when that doesn't exist. Tarl N. (discuss) 19:30, 19 August 2020 (UTC)
Observations of a number of stars orbiting around Sagittarius A*, most notably the star S2, have been used to provide evidence for the presence of, and produce data about, the Milky Way's hypothesized central supermassive black hole, and have led scientists to conclude that Sagittarius A* is beyond any reasonable doubt the site of that black hole.Do we want to trim that down, or just leave it as is? Tarl N. (discuss) 19:56, 19 August 2020 (UTC)
Observations of a number of stars orbiting around Sagittarius A*, most notably the star S2, have been used to provide evidence for the presence of, and produce data about, the Milky Way's hypothesized central supermassive black hole. Scientists have concluded that Sagittarius A* is beyond any reasonable doubt the site of that black hole.Schazjmd (talk) 20:03, 19 August 2020 (UTC)
Sounds like consensus. Updated the lede accordingly. Tarl N. (discuss) 16:12, 21 August 2020 (UTC)
Well I should have waited one month. Yesterday the Nobel Prize in Physics was awarded to Andrea Ghez and Reinhard Genzel specifically for demonstrating that Sagittarius A* is a black hole. Twenty hours later I came here to this article, and now the consensus result of this talk-subsection has been voided and all qulifiers-of-doubt, that Sagittarius A* is a black hole, have been removed from this article. I was correct in stating, 48 days ago, that "This issue is entirely settled."Nick Beeson (talk) 13:52, 7 October 2020 (UTC)
In this and a number of articles, for example "Supermassive black hole", it is written "the Milky Way galaxy has a supermassive black hole at its center" or similar. Can we conclude that the black hole is the center of the Milky Way. The center of the galaxy should be defined as the point which everything rotates around, and that has to be the black hole, or?--BIL (talk) 10:55, 11 October 2020 (UTC)
There's been some back-and-forth on the huge table in the Orbiting Stars section. Might I suggest that table (and associated text) could move into its own article (e.g., Sagittarius A* cluster), leaving only a few example stars in this article? Tarl N. (discuss) 02:36, 14 October 2020 (UTC)
References
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As a side note, we should probably update the 2011-era diagram of the star cluster orbits - those stars are no longer the most interesting. I chose the stars to remain in the local table based on presence in that diagram, but it's fairly obsolete. The "S62 and S4711..." article above has a current diagram on page 6, but I'm not sure of the ins-and-outs of making a new diagram based on that. Even trying to upload a screen shot for discussion defeated me (I tried "fair use", and it refused to allow fair use on a talk page). Tarl N. (discuss) 02:43, 19 October 2020 (UTC)
I'm about to remove this citation: ref>Marongwe, Stuart (19 December 2018). "A Covariant Canonical Quantization of General Relativity". Advances in High Energy Physics. 2018: 1–7. doi:10.1155/2018/4537058. ref> I think it's dubious. I got very excited by the title, as that would be one heck of an achievement. So I sat down to read the paper... It's got a decent intro ... and mentions a long string of correct keywords. But they are just that ... strings of keywords, followed by their textbook definition. Like ... gamma matrices ... is the author really unaware of spin connections which is what he seems to be struggling to explain? Or vielbeins, which is what he seems to want to make use of? We've got articles in WP on this stuff. It's just not that hard or complicated. Beyond the bare-bones definitions, nothing in that paper is articulated. The eqns aren't connected to each other. I agree that the paper lists mostly all of the appropriate, plausible ingredients that one might need for a "covariant canonical quantization", but the paper doesn't actually do that. It' doesn't do what the title (and abstract) claim. By the last 1/3rd of the paper ... about entropy and bits, the stuff about Sag A* seems .. utterly implausible. If I've missed something here, and someone could explain it, I'd love that (not joking; I know this material.) 67.198.37.16 (talk) 00:06, 15 November 2020 (UTC)
I added... "Supermassive black holes are characterized by just two numbers: mass and spin, but have a critical influence on the formation and evolution of galaxies. The spin of Sagittarius A*, a 4-million-solar-mass black hole at the center of our Milky Way Galaxy...'For our study we used the recently-discovered S-stars to show that the spin of Sagittarius A* must be smaller than 10% of its maximal value, corresponding to a black hole spinning at the speed of light,' (~30,000 km per second/~18,628.2 miles per sec)" - Harvard University Professor Avi Loeb<ref]Astrophysical Letters</ref] and http://www.sci-news.com/astronomy/sagittarius-a-spin-08993.html#:~:text=The%20spin%20of%20Sagittarius%20A%2A%2C%20a%204-million-solar-mass%20black,the%20distribution%20of%20the%20S-stars%20in%20its%20vicinity. 2601:589:4801:5660:E8CC:F2F6:C703:980C (talk) 01:36, 12 June 2021 (UTC)
The article text referencing the date of the chart showing the cluster of stars around SgrA* indicates 2011, but the chart itself indicates 2005 on the footnote. I am easily confused, but from what date is the data on the chart - are the orbits and coordinates shown on it from 2005 or 2011? Tesseract501 (talk) 05:47, 30 November 2021 (UTC)
G2 appears not to be a dust cloud but consists likely of three protostars (age less than 1 My) within a dust cloud. For this reason G2 was not destroyed at its approach to Sgr A*.
--Ernsts (talk) 17:10, 14 December 2021 (UTC)
There's already confusion in the edit history about this, which I noticed because I wanted to go in and correct the date on the picture before I realised I was wrong. Both the image capture and image release date are mentioned in the article but it's not in context of each other. Could somebody re-write the final paragraph in the lede so it's not confusing to people reading that and looking at the picture on the right and being very confused? Same goes for the final paragraph in the first section of the page. I'd edit it myself but I don't understand the technical details and so lack the knowledge to phrase it correctly.
137.111.13.103 (talk) 01:59, 13 May 2022 (UTC)
The last paragraph of the introduction says " ... released a photograph of Sagittarius A* ...". Wouldn't "image" be more accurate than "photograph"? Bubba73 You talkin' to me? 03:36, 14 May 2022 (UTC)
Can someone please clarify whether the excitement mentioned in the lede, in the above statement, means that the discovery was "exciting" to astronomers and the general public, i.e. wonderful, brilliant news, or whether "exciting" is a technical term related to the term "excited state"? - BobKilcoyne (talk) 00:27, 14 May 2022 (UTC)
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Please change the sentence at the beginning of the section "Observation and description":
"On May 12, 2022, the Event Horizon Telescope, for the first time, released a photograph of Sagittarius A*, based on direct radio images which were taken in 2017, and confirming the object to contain a black hole."
to
"On May 12, 2022, the Event Horizon Telescope Collaboration, for the first time, released a photograph of Sagittarius A*, based on direct radio images taken in 2017, and confirming the object to contain a black hole."
Reasoning: A telescope cannot release a photo, astronomers can. The sentence can be simplified, by removing the phrase "which were". 109.241.162.167 (talk) 18:59, 15 May 2022 (UTC)
The first sentence of the article body begins "On May 12, 2022, the Event Horizon Telescope Collaboration, for the first time, released an image of Sagittarius A* ...". I can't parse what "for the first time" is supposed to mean in this sentence. I think, based on my general knowledge rather than based on the sentence itself, that it's supposed to mean this is the first image ever produced of Sgr A* by anyone. But it reads more like it's saying this is the first time that this collaboration has released an image of Sgr A*, or possibly that it's the first time that this collaboration has released an image of any black hole, or even that it's the first time they've released any image. I'm not sure what's intended, so I'd ask that someone who knows what is intended here fix the wording to be less ambiguous. CodeTalker (talk) 17:47, 16 May 2022 (UTC)
On May 12, 2022, the first image of Sagittarius A* was released by the Event Horizon Telescope Collaboration. The image, which is based on radio interferometer data taken in 2017, confirms that the object contains a black hole.Schazjmd (talk) 17:53, 16 May 2022 (UTC)
Sgr A* is 26,000 light-years from earth, and a circumference of a circle with that radius is 2pix26,000 light-years = 163,363 light years (ly). A light year is 2.998x10^8 m/s x 365.24 days/year x 24 hours/day x 3600 s/hour = 9.461x10^15 m. An arc-degree is 1/360 of the circumference, and a micro-arc-second is (1/3600)x10^-6 of that, resulting in a diameter of 163,363 ly x 9.461x10^15 m/ly x 51.8 x 10^-6/(360x3600) = 6.18x10^10 m, not 5.18x10^10 m. This also results in 38.4 million miles, not 32.2 million miles. — Preceding unsigned comment added by Delbert7 (talk • contribs) 14:08, 10 February 2023 (UTC)
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Sagittarius A* is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6 degrees south of the ecliptic, visually close to the Butterfly Cluster and Lambda Scorpii. On May 12, 2022, astronomers released this first image of the accretion disk around the event horizon of Sagittarius A*, produced in April 2017 by the Event Horizon Telescope (EHT), a worldwide network of radio observatories, confirming the object to be a black hole. This was the second confirmed image of a black hole, after EHT's image of M87* released in 2019. Image credit: EHT Collaboration
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This section of the article is disproportionately long compared to other objects orbiting Sagittarius A*, so I'd recommond splitting this content to a new article on top of the redirect G2 gas cloud. –LaundryPizza03 (dc̄) 09:55, 4 April 2023 (UTC)